I'm not sure that's always true. For example, in my field, mathematics, there are a lot of results that are much easier to explain and learn then they were to discover.

With any NP problem, it's much easier to verify the result than to come up with it. What you describe probably fits this pattern.

In economics, the problem is not that established results, or even open problems, are easy to explain. The problem is that credentialed experts keep arguing about toy problems that are easily explained to a layman, and are unable to produce any insight beyond what an intelligent layman would also be able to figure out quickly. What's more, they can't even reach consensus that the problem is intractable, each arrogantly claiming that his ideologically favored theory is correct, and his opponents disagree because they are delusional or dishonest charlatans. (The latter is usually expressed more diplomatically, though it's actually quite common even for top-rank economists' writing to drip with unconcealed scorn and contempt of the most arrogant sort.)